Two dimensional microwave chemical flood testing means and method

ABSTRACT

A method of two dimensional chemical flood testing includes evacuating a porous medium contained in a test cell. The porous medium in the test cell is irradiated with a beam of microwave energy at a plurality of predetermined locations on said test cell. The microwave energy that has passed through the porous medium at each location is detected at the location. The porous medium in the test cell is filled with brine. The irradiating and detecting steps are repeated, the porous medium is then flooded with crude oil, or a substitute, and again the irradiating and detecting steps are repeated. The porous medium is flooded with brine and again the irradiating and detecting steps are repeated. A calibration curve for each location is derived from the detected microwave energy at the location from the prior irradiating and detecting steps. The chemical flood system is tested by flooding the porous medium with the chemical flood system at a predetermined flow rate during which time the irradiating and detecting steps are repeated periodically so that the test cell is periodically scanned in two directions by microwave energy. A two dimensional pattern of the chemical flood is derived for each scan in accordance with the detected microwave energy at each location for the scan and the calibration curves.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to means and methods for chemical floodtesting and, more particularly, to chemical flood testing usingmicrowave energy.

2. Description of the Prior Art

Chemical flood core testing in a linear or single direction is disclosedand described in U.S. patent application Ser. No. 336,142 now U.S. Pat.No. 4,490,676 12/25/84 and application Ser. No. 336,136, now U.S. Pat.No. 4,482,634 11/13/84 both filed on Dec. 31, 1981 and assigned toTexaco Inc., assignee of the present invention. The practice heretoforehas been to take the linear flow data from a long core flood test andthrough known mathematical techniques predict a two dimensional chemicalflood in a pattern in an oil reservoir. The present invention is capableof actually measuring a two dimensional chemical flood through a porousmedium that may be used to either supplement and prove the predictionsbased on the linear flow testing or it may be used independently of thepredictions as another step in chemical flood testing.

SUMMARY OF THE INVENTION

The means and method of a two dimensional chemical flood testingincludes evacuating a porous medium contained in a test cell. Theevacuated porous medium is then irradiated with a beam of microwaveenergy in said test cell in a plurality of predetermined locations ofsaid test cell defined by a two-axis coordinate system. The microwaveenergy that has passed through the porous medium at each location isdetected. The porous medium is then filled with brine and theirradiating and detecting steps are repeated. The porous medium is thenflooded with crude oil, or its substitute, and again the irradiating anddetecting steps are repeated. The porous medium is flooded with brineand, again, the irradiating and detecting steps are repeated. Acalibration curve for each location is derived from the detectedmicrowave energy at the location from the prior detecting steps at thelocation. The porous medium while being flooded with a chemical floodsystem at a predetermined flow rate is periodically subjected to theirradiating and detecting steps so that the test cell is periodicallyscanned in two directions by microwave energy. A two dimensional patternof the chemical flooding is derived for each scan in accordance with thedetected microwave energy at each location for the scan and thecalibration curves.

The foregoing and other objects and advantages of the invention willappear more fully hereinafter from consideration of the detaileddescription which follows, taken together with the accompanying drawingswherein one embodiment of the present invention is illustrated by way ofexample. It is to be expressly understood, however, that the drawingsare for illustration purposes only and are not to be construed asdefining the limits of the invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial representation in combination with a simplifiedblock diagram of a microwave chemical flood scanner constructed inaccordance with the present invention.

FIG. 2 is a detailed block diagram of the electrical portion of themicrowave chemical flood scanner shown in FIG. 1.

FIGS. 3A and 3B are an end view and a side view, respectively, of themechanical portion of the microwave chemical flood scanner shown in FIG.1.

FIG. 4 is a top view of the test cell shown in FIGS. 1 and 2.

FIG. 5 is a simplified block diagram of the hydraulic system of themicrowave chemical flood scanner shown in FIG. 1.

DESCRIPTION OF THE INVENTION

U.S. patent applications, Ser. Nos. 336,136 and 336,142, filed on Dec.31, 1981 by the inventors of the present invention which is assigned toTexaco Inc., assignee of the present invention, relate to chemical floodevaluations being made on cores of an earthen reservoir to evaluate thechemicals used. It is possible with the information from those analysesto project and predict a flood pattern of a particular chemical floodsystem through a reservoir. A chemical flood system is a flood systemusing one or more liquid chemicals in conjunction with a drive liquid.The drive may be a liquid or it may be water or brine. Often, afive-spot operation is used in enhanced oil recovery; i.e., four wellsdefining substantially a horizontal square with a fifth well in thecenter of the square. Thus, with a given injection well, there is athree dimensional flow of chemicals and drive liquid through thereservoir vertical, traverse and longitudinal. Since the chemical floodanalyses of the aforementioned U.S. applications deal with only onedimension or direction, the present invention using two-dimensionalmonitoring yields more information in regard to a two dimensional flowpattern that the liquids will follow.

With regard to FIG. 1, a rectangular porous medium in a test cell 3, andany liquid flowing through it, is subjected to a beam of microwaveenergy by a microwave transmitter 5, as hereinafter explained, whichpasses through the test cell 3 and is detected by detector assembly 8.Microwave energy is herein defined as being electromagnetic energyprovided at a microwave frequency. Microwave transmitter 5 receives thenecessary operating voltages from voltage sources 10 and 11. The outputfrom detector assembly 8 is provided to a controller 14 which providesinformation to computer 15.

Liquid means 20 causes different liquids at different times to beinjected into test cell 3, as hereinafter explained, at a predeterminedvelocity which will eventually flow through test cell 3 and enterreceiving means 24. As the liquid passes through test cell 3, microwavetransmitter 5 and detector assembly 8 are maintained in fixedrelationship to each other but are moveable in an x direction and in a ydirection under the control of controller 14, and the movement isrepeated during the flowing of the liquids through test cell 3. All ofthe foregoing will be described hereinafter in greater detail.

With reference to FIG. 2, microwave transmitter 5 includes a Gunn source28 receiving a DC voltage from DC source 10 and an AC voltage having apreferred frequency of 1 KHz from AC source 11 and provides microwaveenergy. Gunn source 28 may be of a type that is manufactured by Racon,Inc. as their part number 10014-102-02. The microwave energy is providedat a preferred frequency of 10.525 GHz whose amplitude oscillates at the1 KHz frequency. Source 28 provides the microwave energy to anattenuator 30 which in turn provides the microwave energy to a hornantenna 33 which provides the beam of microwave energy. It should benoted that a horn antenna is used because Gunn source 28 is beingoperated in an X-band mode mainly in 8.2 to 12.4 GHz.

It may be desired to operate Gunn source 28 at a preferred frequency of24.125 GHz which is in the K-band range of frequency namely 18.0 to 26.5GHz. Operation in the K-band mode makes monitoring of the liquid passingthrough test cell 3 more independent of temperature and salinity. Thedetermination of whether to use X-band or K-band is also in partdetermined by the thickness of the formation being tested. A preferredpower output for the X-band is 10 milliwatts or for the K-band, 20 to100 milliwatts, are safe operating levels. When operating in a K-band,horn antenna 33 is replaced by a dielectric rod antenna and Gunn source28 is of a type similar to that manufactured by Plessey Optoelectronicsand Microwaves, Ltd. as their part GDO131. Further, the AC source may beomitted in K-band operation and an isolator is substituted forattenuation pad 30.

The microwave energy passing through sample cell 3 is received byanother horn antenna 36 of detector assembly 8, in X-band mode ofoperation, or a dielectric rod antenna in a K-band mode, and provided toa diode detector 38 which provides a signal corresponding to thedetected microwave energy to a power meter 40. Power meter 40 providesan indication of the detected microwave energy and a measurement signalto controller 14 which in turn provides the measurement signal tocomputer 15 and to a printer 43. Controller 14 includes acomputer/controller 44 connected to power meter 40 and receiving thesignals therefrom, and, in turn, provides a signal to printer 43 and tocomputer 15. Computer 15 may be a general purpose digital computer, theequivalent of International Business Machine Corporation's computer.Computer/controller 44 may be of the type manufactured byHewlett-Packard as their model number H-P85. Associated withcomputer/controller 44 is a memory 46 having a two-way communicationwith computer controller 44. Computer/controller 44 also has two-waycommunication with data/acquisition and control unit 50 which may be ofthe type manufactured by Hewlett-Packard as their model number H-P3497A.Data acquisition and control unit 50 utilizes the information fromcomputer/controller 44 to send information necessary to the movement andcontrol of microwave transmitter 5 and detector assembly 8.

Referring back to FIG. 1 and to FIGS. 3A, and 3B, the apparatus ofmicrowave transmitter 5, detector assembly 8, and test cell 3 aremounted on apparatus which is basically a combination of units of thetype manufactured by Velmex Inc. under their part numbers B6000 andB4000. The combination of two belt coupled B6000 units and a B4000 unitgives the operation two dimensional movement. A housing 54 houses theGunn source 28 and attenuation pad 30 and is affixed to a rod 57. Theelectrical connections to DC source 10 and AC source 11 are not shown.Test cell 3 is mounted on a fixed body 60. Antenna 36 is connected todetector 38 supported by arms 62 and 63 with detector 38 being locatedin a housing 66 mounted to a rod 58 and engaging a screw rod 79. Rods 57and 58 are maintained in a fixed relationship to each other by endbrackets 70, 71 and are controlled to slide through mountings 74 and 75so as to move antennae 33 and 36 along one direction (x direction) ofsample cell 3 by screw rod 79 driven by a stepper motor 80. Members 74and 75 are controlled to move in another direction (Y direction) by astepper motor 96 along slides 81 and 81A (not shown) by screw rods 84and 84A (not shown), respectively.

Referring again to FIG. 2, data/acquisition and control unit 50 controlsan X axis preset indexer 84 and in turn receives information as to itsindex position. An X axis limit switch 86 provides a signal to X axispreset indexer so as to prevent microwave transmitter 5 and detectorassembly 8 from exceeding a predetermined x distance. X axis presetindexer 84 provides a signal to X axis stepper motor 88 to control thepositioning of the X axis of microwave transmitter 5 and detectorassembly 8. Similarly, data/acquisition and control unit 50 provides asignal to and receives a signal from Y axis preset indexer 94. Indexer94 also receives a signal from Y axis limit switch 98 so as to preventmicrowave transmitter 5 and detector assembly 8 from exceeding a Ydirection limit. The Y axis preset indexer provides a signal to Y axisstepper motor 96 to control movement in the Y direction. X axis positionreadout potentiometer 100 and Y axis position readout potentiometer 101receive energizing voltages from DC power supplies 104 and providessignals to data/acquisition and control unit 50 corresponding to thelocation of microwave transmitter 5 and detector assembly 8 in the Xdirection and in the Y direction, respectively.

With reference to FIG. 2 and FIG. 4, the cross-sectional portion of testcell 3 shows a porous formation 120 coated with epoxy 122 and 123.Formation 120 may be an actual earth formation or it may be a fabricatedformation. One such fabricated formation is an oil-wet, homogeneous,synthetic consolidated porous material composed of spherical glass beadsepoxed together. A matrix of this type is manufactured under the name,Tegraglas Porous Structures, grade 15, which is the least permeable formcurrently available, has a very uniform pore size of 16-17 μm, apermeability of 1-2 darcies, a porosity of about 30%, and a surface areaof only 0.057 m² /g. As shown in FIG. 4, the sample cell issubstantially square, two opposite corners are chamfered to have a 45°corner, and a simulated wellhead is connected to each chamfered corner.Each wellhead 130 or 132 has internal passageways adapted to acceptconventional type chromatograph fittings. The resultant model is 1/4 ofa 5-spot pattern; that is, the center well and one corner well of aconventional 5 -spot configuration.

Referring now to FIG. 5, liquid means 20 include pump means 139 whichpumps distilled water through valve means 140. Valve means 140 inconjunction with valve means 142 in effect controls which liquid isgoing to be provided to test cell 3 by way of well 130. In one mode, theoutput from valve means 140 is provided to a crude oil, or a substitutesource 144. One such substitute may be a predetermined mixture of freshwater and 2-propanol. In another mode, valve means 140 providesdistilled water to a surfactant source 145, in yet another mode, theoutput from valve means 140 is provided to a polymer source 146, and ina fourth mode results in valve means 140 output being provided to abrine source 147. Each source, 144, 145, 146 or 147 includes aconventional type free floating piston (not shown) in a container (notshown) having either a crude oil or a substitute, or surfactant, orpolymer, or brine. The pumped-in distilled water causes the piston toexpel a corresponding amount of liquid (crude oil or its substitute,surfactant, polymer or brine). The output of crude oil source 144,surfactant source 145, polymer source 146 and the brine source 147 areprovided to four different inputs of valve means 142. Thus for one mode,pump means 139 in effect pumps crude oil, or its substitute, from crudeoil source 144 into test cell 3; in the second mode surfactant fromsurfactant source 145 is pumped into test cell 3; while in a third mode,pump means 139 in effect pumps polymer from polymer source 146 into testcell 3, and for the fourth mode, brine is pumped into test cell 3.

The liquid from valve means 142 passes through test cell 3 to anothervalve means 150 in receiving means 24 by way of well 132. Valve means150 is operated in conjunction with valve means 140 and 142 to passliquid from test cell 3 to liquid receiving means 156, 156A, 156B or156C. It should be noted that elements having the same numericalidentification with a different suffix are operated and are connected ina similar manner as the element with the same numerical designationwithout a suffix.

The present invention may be operated in the following manner. Test cell3 is completely evacuated and the apparatus of the present invention isoperated to position microwave transmitter 5 and detector assembly 8 inpredetermined locations so as to make microwave measurements at thoselocations in a predetermined sequence. It does not matter in whatsequence the various locations are subjected to the microwavemeasurements, but obviously it is easier for programing and comparisonto use the same sequence whether the test cell 3 is completely evacuatedor is in the process of a test. These first measurements correspond tothe porous material 120 of test cell 3 being filled only with crude oil.Test cell 3 is then flooded with brine from source 147 through theoperation of pump means 139, valve means 140, 142 and 150 and wells 130and 132, and, a second set of microwave measurements are made andprovided to computer 15 so that a second set of measurements correspondto the brine in test cell 3. Pump means 139, valve means 140, 142 and150 are again operated to inject crude oil, or its substitute, into testcell 3 until only crude oil, or its substitute, leaves test cell 3 andthen microwave transmitter 5 and detector assembly 8 are operated tomake measurements at the predetermined locations. This third set ofmeasurements corresponds to residual brine to oil at the differentlocations or in the case of the crude oil substitute, corresponds to anequivalent oil saturation. Pump means 139, valve means 140, 142 and 150are again operated to inject salt water into test cell 3 until only saltwater leaves test cell 3. Microwave transmitter 5 and detector assembly8 are then operated to make the measurements at the predeterminedlocations. This fourth set of measurements corresponds to the waterflood residual oil at the different locations. The four measurements ateach location are used to derive a calibration curve for each location.The calibration curves are generated by computer 15 utilizingconventional curve generation techniques. In some cases, softwareprograms for computer 15 may be purchased from companies thatmanufactured the computer 15, such as International Business MachineCorporation.

At this point, the actual testing of the chemical flood now commences.It should be noted that in chemical flooding many combinations can beutilized. For example, and this is not truly a chemical flood, brine maybe used to drive the oil from the injection well to the producing well,which is a water flood. In chemical flooding techniques a surfactant isused, sometimes driven by brine, or sometimes driven by a polymer.Another alternative to the combination would be a surfactant followed bya polymer driven by brine. Thus, various combinations of liquidchemicals with or without brine may be used in the field. It should benoted that although the term brine is used, it is meant that a water isused, and preferably a water solution with a chemical compositionsimilar to that of the water in the actual oil reservoir or the waterthat will be used to drive the chemical flood.

In one mode of chemical flooding, pump means 139, valve means 140, 142and 150 are operated in a sequence so that a slug of surfactant fromsource 145 followed by a slug of polymer from source 146 and driven bybrine is injected into test cell 3 by way of well 130 so that the oilremaining in test cell 3 after the water flood of the calibrationprocess is driven to producing well 132. While this is going on,microwave transmitter 5 and detector assembly 8 are operated in a mannerso that they will provide microwave measurements to computer 15 for eachlocation in a predetermined pattern. One such pattern is to divide testcell 3 into a plurality of smaller areas and the microwave transmitter 5and detector assembly 8 are positioned at each area. Each area isirradiated with microwave energy with detector assembly 8 detecting theenergy passing through that area to provide its reading, the sequencebeing that each area adjacent to well 130 is measured initially and thenext adjacent area is read, and so forth progressing away from well 130so as to scan test cell 3. This scanning operation is repeatedthroughout the cell 3 will be scanned 20 times in the predeterminedsequence during the test time.

The slug sizes of surfactant and polymer are predetermined and may varyfrom test to test at the desire of the operator. The flow rate of thechemical flood is scaled to approach the reservoir flood velocity. Thetypical reservoir flood velocity might be one foot per day. Computer 15can then provide either or both a printout of the microwave readings ateach location for each scan and a two-dimensional graph of test cell 3showing the distribution of the oil as it moves through test cell 3.Again, each graph or plot would be made after each scan during thechemical flood test. It is also feasible to generate the plots or graphsat the end of the chemical flood test since the data is stored duringtesting.

The present invention as hereinbefore described is a microwave scannerthat monitors the chemical flooding of a test cell representative of onequarter of a five spot enhanced oil recovery operation. The presentinvention is not restricted to five spot operation analysis, but is alsoapplicable to any enhanced oil recovery utilizing chemical flooding withat least an injection well and a producing well.

What is claimed is:
 1. A microwave chemical flood scanner comprising:atest cell having an entry port and an exit port and containing a porousmedium, said test cell having side dimensions which are substantiallygreater than a thickness dimension of said test cell, liquid sourcemeans for providing different liquids to said entry port, means forreceiving the different liquids from said exit port, transmitter meansfor providing a beam of microwave energy when energized, receiver means,spatially related to said transmitter means in a manner so that saidtest cell may be permitted to be interposed between said transmittingmeans and said receiving means, for receiving a beam of microwave energyafter it has passed through said test cell and providing a signalcorresponding to a characteristic of at least one liquid in said porousmedium in said test cell, means for energizing said transmitting means,means for moving said transmitting means and said receiving means whilemaintaining their spatial relationship in a manner so that the beam ofmicrowave energy will pass through said test cell at a plurality ofpredetermined locations that define a two dimensional pattern on saidtest cell, calibration curve means for deriving and storing acalibration curve for each predetermined location, and means forproviding a graphical representation of the liquid content of saidporous medium in said test cell in accordance with the signal from thereceiving means, stored calibration curves, and the positioning of thetransmitter means and receiver means in relation to the locations on thetest cell; said moving means includes first mounting means for havingsaid test cell mounted upon it for holding said test cell in a fixedposition, second and third mounting means, for having the transmittermeans mounted on the second mounting means and for having the receivingmeans mounted on the third mounting means in a manner so that they arealigned with each other and having sufficient space between them so thatsaid test cell may be interposed between said transmitter means and saidreceiver means, first means for moving said second and third mountingmeans in unison along an X axis, fourth and fifth mounting means havingthe first moving means mounted thereon, second means for moving thefourth and fifth mounting means along a Y axis, which is perpendicularto the X axis, and means for controlling the movement of the second andthird mounting means and the fourth and fifth mounting means so that thetransmitter means and the receiver means will stop temporarily atpredetermined locations on the test cell for the microwave irradiationthrough the porous medium at that location; and said liquid meansincludes: pump means for pumping a non-corrosive liquid, a crude oil, ora substitute, source, a surfactant source, a polymer source and a brinesource, first valve means connecting said pump means to said crude oilsource, to said surfactant source, to said polymer source and to saidbrine source for controlling the liquid provided by said pump means tobe provided to either the crude oil or substitute source, the surfactantsource, the polymer source, or the brine source so as to displace crudeoil from the crude oil source, surfactant from the surfactant source,polymer from the polymer source, or brine from the brine source; secondvalve means connected to the crude oil source, to the surfactant source,to the polymer source, to the brine source and to the entry port of saidtest cell and cooperating with the first valve means for directing thebrine, the polymer, the surfactant, or the crude oil or its substitute,into said test cell; and the liquid receiving means includes: thirdvalve means for cooperating with said first and second valve means, andconnected to the exit port of said test cell three for providing theliquid flowing from the sample cell to an appropriate container means ora plurality of container means.
 2. A microwave scanner as described inclaim 1 in which the transmitter means provides a beam of microwaveenergy at a frequency in the X-band frequency.
 3. A microwave scanner asdescribed in claim 2 in which the transmitter means is energized by theenergizing means at each location and not while it is moving fromlocation to location.
 4. A microwave scanner as described in claim 1 inwhich the microwave transmitter means provides a beam of microwaveenergy at a frequency in the K-band.
 5. A microwave means as describedin claim 4 in which the transmitter means is energized by the energizingmeans at each location and not while it is moving from location tolocation.